1. Field of the Invention
This invention relates generally a laser with a temperature controller that maintains the gain medium at a temperature of 25 degrees C. or greater, and more particularly to a laser with a temperature controller that is positioned in the laser head.
2. Description of Related Art
The optical pump process in a solid-state laser gain medium is associated with the generation of heat. Efficient heat removal and reduction of the thermal effects which are caused by the temperature gradients across the active area of the gain medium often dominate design considerations for high-average-power systems.
Surface cooling of the gain medium has been utilized to remove heat. The combination of volumetric heating of the gain medium by the absorbed pump radiation and surface cooling required for heat extraction leads to a nonuniform temperature distribution in the gain medium. This can result in a distortion of the output beam due to a temperature and stress-dependent variation of the index of refraction. The thermal effects occur in the gain medium are thermal lensing and thermal stress-induced birefringence.
An additional issue associated with thermal loading is stress fracture of the gain medium. Stress fracture occurs when the stress induced by temperature gradients in the gain medium exceeds the tensile strength of the material.
Temperature gradients generate mechanical stresses in the gain medium, since the hotter inside area is constrained from expansion by the cooler outer zone. Optical distortions are a result of both temperature gradients and stresses.
Cooling of the gain medium can be achieved with liquids and gases. Conductive cooling is used by mounting the gain medium directly to a heat sink.
These methods are expensive. Additionally, these methods do not provide for control of gain medium temperature.
There is a need for a laser with a temperature controller positioned in the laser head. There is a further need for a laser with a temperature controller that maintains the gain medium at a temperature of 25 degrees or higher.